The swelling pressure of the surrounding rock in tunnels within expansive soil significantly escalates construction risks and poses a threat to overall tunnel stability. Addressing this concern, this paper has formulated calculation methods suitable for analyzing the stability of tunnels in expansive soil, taking into account swelling pressure. These methods were developed based on the convergence-confinement and empirical methods. Furthermore, measurements of surrounding rock pressure and displacement were conducted in a deep-buried tunnel within the expansive paleosol of the Chinese Loess Plateau. These measurements aimed to evaluate the suitability of the derived calculation methods. The effects of both the surrounding rock swelling pressure and support parameters on key factors such as surrounding rock pressure, displacement, and safety were thoroughly analyzed. The outcomes demonstrate that the convergence-confinement method, when considering swelling pressure, is highly relevant for assessing the stability of tunnels in expansive soil characterized by structural strength and good integrity. This approach also proves effective in evaluating the stability of tunnels situated within the expansive paleosol of the Chinese Loess Plateau. Conversely, for tunnels in expansive soil with low strength and poor integrity, the application of Protodyakonov’s theory, Terzaghi theory, and the Code method, all accounting for swelling pressure, proves to be suitable for stability analysis. In expansive paleosol tunnels, as the surrounding rock swelling pressure increases from 0 kPa to 400 kPa, the safety factor of the surrounding rock pressure decreases by more than 0.17, whereas the safety factor of the surrounding rock displacement decreases by less than 0.05. Furthermore, when optimizing the parameters of steel set spacing, steel set type, and shotcrete lining thickness, it was observed that the safety factor of the surrounding rock pressure increases by more than 0.2, while the safety factor of the surrounding rock displacement experiences an increase of less than 0.15.